Though the aging process is often beautiful, it's never pretty. Time takes its toll on us all and there's never been very much we can do about it. This isn't necessarily true for all organisms, though. Take the sea urchin, for example — some species live to extraordinary old ages with no signs of poor health and they can even quickly re-grow damaged spines and feet. And this regenerative capacity comes with no increase in age-related mortality. Now scientists are studying these remarkable creatures to discover whether they are willing to share some of their secrets with us.
Professor James A. Coffman is studying the way sea urchins age in the hope that a deeper knowledge of the close genetic relationship we humans have with them will lead to a breakthrough in the understanding of the same process for us. In a paper in the journal Aging Cell co-authored by Dr. Andrea G. Bodnar of the Bermuda Institute of Ocean Studies, Coffman suggests that the physical decline that typically accompanies aging is not inevitable.
The scientists studied how regeneration works in three species of sea urchins each with a different life expectancy. The variegated sea urchin, Lytechinus variegatus, has the shortest lifespan, living only about four years. The purple sea urchin, Strongylocentrotus purpuratus, has an intermediate life expectancy of around 50 years. Meanwhile, the red sea urchin, Mesocentrotus franciscanus, is one of the world's longest-lived organisms with a life expectancy of more than 100 years.
Traditionally, it's been believed that aging is a side effect of the genes that promote growth and development. Organisms that have a low likelihood of continued survival in the wild once they have reproduced experience a rapid decline once they have reached reproductive maturity. Therefore, the scientists expected to find that the power to regenerate would decline fastest in species with shortest lifespan.
To their surprise, however, they found that regenerative capacity was not affected by age and was as consistent in the short-lived species as in those with longer lives. Bodnar and Coffman found that although the variegated sea urchin, L. variegatus, has a much lower life expectancy in the wild than the other two species, it displayed no evidence of a decline in regenerative capacity with age. This suggests that the degenerative decline might not be as strongly tied to life expectancy as we thought.
The scientists are planning future studies to identify why exactly short-lived sea urchins experience negligible age-related decline, and are hoping to investigate the role of the immune system in maintaining youthful function into old age. Because — believe it or not — sea urchins and humans are not too dissimilar at the genetic level, these finding could mean big things for our own health and aging.
"We wanted to find out why the species with short and intermediate life expectancies aged and the long-lived species didn't," says Coffman. "But what we found is that aging is not inevitable: sea urchins don't appear to age, even when they are short-lived. Because these findings were unexpected in light of the prevailing theories about the evolution of aging, we may have to rethink theories on why aging occurs."